Arc welding apparatus



Dec. 23, 1958 H. J. BlcI-IsEL ARC WELDING APPARATUS 5 Sheets-Sheet l Filed Sept. 4, 1953 Dec. 23, 1958 H, J, BlCHsEL 2,866,147

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O7 E i 'I sea 26| W @Ummm w r mums ummm," HUHIIUM Iuhlilu United States Patent O 2,s66,147 ARC WELDING APPARATUS Harry 5. lichsel, lEast Aurora, N. Y., assignor to Westrnghouse Electric Corporation, East Pittsburgh, Pa., a corporation of' Pennsylvania Application `September 4, 195,3S`erial No, 328,629 Claims. (Cl. 321-14) My invention relates Ato arc vwelding apparatus and has particular relation to arc weldinghapparatus f the directcurrent type.

.This invention is, in its specific aspects, based von the direct-current arc Welder disclosed in application Serial No. 357,321 for Direct-Current Arc Welders, filed May 25, 1953, to Emil l. Steinert, Harry. J. Bichseland Ray Verne Lester, and assigned to Westinghouse Electric, Corporation, which Ifwill callhereinafter the Steinert application. To the extent that may be necessary, for the understanding of my invention, the Steinert applicationis included by reference in this applicationandgmade apart of it. Further, to the extent that any invention Inadeby me alone is disclosedinthe Steinert application, this app lication is a continuation-in-part of the Seinert .applicat lon.

The Steinert vapplication discloses an arc weideninelnd-v .las a POIS/phase transformer, ,the primaryfeiwhieh .is-s911- nected to a polyphasesource and Athe secondaryotwh-ich supplies a rectier. The output terminals ofthe rectifier are connected between a welding electrodevand workV-in the usual practice of the invention disclosedinthe/Steinert,

through the transformer. The actuating mechanismo the breaker is usually connected l,toconduct,currehtwproportional yto the` current `which Ellovvsvthrough',the lprimary of the welding transformer, and `whenuthis. currentfbecornes excessive, it operatesthe circuit breaker. i

Ihave found` that this prior art apparatus ,isn otalto-l gethersatisfactory. Its principal disadyantageanises from the fact that welding apparatus isus'u'ally' designed Kbe operatedfrom power sources of diife'rentvoltagemagnitude. Since the primaryadrawsydiierent current Aoijlthe different voltages, and the actuatingnmechanisrn canL be set `to respond `to overloads corresponding 'onlyfto` one v.or the other of the currents, the prior art apparatus Ais inadequate. Thus when welding apparatus is supplied from a 220 volt source and is drawing 30.0arnperesloadcurrent, the primary draws of .therorder of 5 Sampercs while,n when weldin g apparatus is supplied from .a .440 volt source, the primary draws only 2,9 amperes for thesameloadcurrent. `Protective ,apparatus of the prior art typein which the actuating mechanismY is .set to operate when'the',' apparatus is supplied from 22() volts ,will failto operate for an overload when the apparatusis `adapted tofbesupplied from 440 volts. The saine conditions arise lfor Athe other voltages at `which the apparatus may 'be designed to operate.

It is accordingly an objectof my invention V to provide are welding apparatus which shallbe effectively .and rev In direct-current 4 H7primary` vwindings andthe secondary-reactor windings.

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liably protected against overload conditions independently of the voltage at which it is operating.

Anotherobject of my invention is to provide arc welding apparatus including overload protective facilities of simple and low-cost structure.

A further object of my invention is to provide rectifier apparatus which shall be effectively and reliably protected by a low-cost protective system.

An incidental4 object of my invention is to provide rectier apparatus having novel protective facilities.

Industrial welders are rated on a duty cycle basis. Thus a 400 ampere welder is designed to deliver 400 amperes at 40 volts load potential on a 60% duty cycle; that is 6 minuteson andW 4 minutes o repeated every 10` min- .utes. Iny addition provisions are. incldued to enable the operator to se't awelder to supply at least 125% ofrated current.

In4 anriving atl my invention I havek realized that one of the .principal purposes of protective` apparatus is to protect, the, Welders fromoverheating which arises from this practice; that is, the protectiveA apparatus is to protect a welder; such as is disclosed in thev Steinert application against he overheaing of thewindings and insulation of the transformer, andl of the rectier which occurs during operation at too high aduty cycle,too high ak current setting-Ory th; That such overheatingmay. be Vsubstantial can belre'alized by consideringn the,v above mentioned 400 amperewelder, A 40u-ampere weldenoperated ,on a 60% dutyl cyclebasis delivers only 310 amperes continuously. 1ff thisl welderk were operated continuously at 400 amperes ithe` heat ,developed ywouldbe d@ 21 3l() times the ratedheat orabout 67% more than rated power. If the same Welder were operated at current` setting it would draw 500 amperes or develop about.56% more thany rated heat. l

Another purpose of the protective apparatus 1sto protect it againstoverheating when the cooling fan 1s turned oi.

My invention arises from the discovery, as .a result of extended investigation and study, that arc welding apparatus as disclosed jin the Steinert application and apparatus similar to itwmay be effectively protectedagainst'overheating particularly in the situations just mentioned by a single thermally actuable element disposed to respond to a temperatureof a region of the apparatuswhich develops heat at a rate critically representative ofthedevelopment 'of heat in the other important parts of the apparatus. This element may be actuated at a temperature of the critical region which is reached, beforedangerous ternperatures are reached in the other parts of the apparatus. Specifically, I have found that the thermally actuable elements'hould be mounted in intimatecontact with a portion ofthe transformer, either with the primary or with'the secondary reactor, but preferably in contact with anpor-tionlof the turns of a'secondary-reactor ,-winding of thetransformer. My investigation-has revealed that a thermally actuable element set to open whenthis rcgionvapproaches a criticaltemperature opens ata'time when the other portions of the apparatus, such as the rectieror? the other parts of the transformer, are Well below any dangerous temperatures.

'ln' conducting the study which'has givenrisev to my invention'` as just described, I have considered in detail withthead of elaborate measurementsv the thermaland electrical properties of the various vulnerable parts of the apparatus. These parts are principally the rectifier, the

The rectifier is usually of the dry type and is an assembly f Steinert application.

3 made up of a number of rectifieT U'ITS 0r stacks. The mass of the rectifier assembly is i'mively 10W and the rectifier would then tend to heat up @relatively high rate. However, the rectifier elements? Oflthe stacks are provided with fins and the stacks are relatively .widely spaced so that the emission of heat from" the rectifier by radiation, conduction and convection is lrelatively high. When the rectifier is subjected to conditions* tending to increase its temperature, then, it tends to reach arel'atively stable temperature in a short time and the temperature. of the rectifier begins to level off soon after it is subccted to the conditions tending to increase the temperature andz (the danger to temperature for the rectifier is approached gradually slower. A

The various components of the transformer are massive.; When the transformer is subjected to conditions tend?- to increase its temperature this temperature rises slowA But the turns of the windings of the transformer are closesly associated and are enclosed in insulation and the heats; flow from the transformer by reason of radiation, convec`- tion and conduction is not at a high rate. .The trans-- former then has a tendency to rise in temperature at a sub-- stantial rate which may in fact increase as the heating continues. My study has further revealed that certain portions of the secondary-reactor winding of the transformer rises at a substantially higher rate than the primary or other portions of the secondary-reactor. ln accordance with the specific aspects of my invention then, the thermal element which actuates the circuit interrupting means is for this reason mounted in intimate thermal contact with certain of the turns of the secondary.

A further aspect of my invention arises from the real-t-- ization that the thermally actuable element once operated tends to cool' down relatively slowly so that it prevents reclosing of the circuit interrupting means of the appara-V tus a short time after it is opened. To facilitate resetting of the apparatus a short time after operation of the circuit interrupting means, the circuit for tripping the interrupting means is provided with a switch which may be actuated to permit operation independently of the thermally actuable means.

The novel features that I consider characteristic of my invention are set forth generally above. The invention itself, both as to its organization and its method-of opera-` tion, together with additional objects and advantages thereof may be understood from the following description of a specific embodiment when read in connection with the accompanying drawings in which:

Figure l is a circuit diagram of an arc Welder in accord?- ance with my invention;

Fig. 2 is a view in transverse section with certain parte` broken away of an arc Welder in accordance with my in-I vention showing the welding transformer and its associated parts;

Fig. 3 is a view partly in front elevation and partly in transverse section of the lower portion of the arc Welder shownl in Fig. 2 with the Wall of the cabinet removed;

Fig. 4 is a view in plan, enlarged, of the rectifier assembly included in the arc welder shown in Fig. 2 and Fig. 3;

Fig. 5 is a view in plan of a small portion ofthe secondary-reactor of the arc welder shown in Fig. 2;

Fig. 6 is a view in section taken along line VI-VI of Fig. 5;

Fig. 7 is a graph presented to aid in explaining my invention; and

Fig. 8 is a fragmentary view showing a modification of my invention.

Fig. 2 is similar to Fig. 2 of the Steinert application,v

and Fig. 3 is similar to the lower part of Fig. l of the So that the relationshipl between this application and the Steinert application may be understood, the labelling of the drawings of the Steinert application is, to the extent practicable, followed in this application.

assenti?- The apparatus shown in the drawings includes a threefphase transformer TR, having primary windings P1, P2 .and P3 and secondary-reactor windings SR1, SR2 and SR3. The primary windings Pl, P2 and P3, and the .secondary-reactor windings SR1, SR2 and SRS, are each -connected in delta. The transformer TR has a fixed Vreluctance core CF and a variable reluctance core CV. 'The fixed reluctance core has cross laminations C1 and -C2 between which legs L1, L2 and L3 extend. The variable reluctance core CV is made up of two equal sections -CVl and C`V2, each of which has a lower fixed part or .assembly A1 consisting of cross lamination C3 and three .stub legs LS1, LS2 and LS3 (only L83 shown; all three :shown in Steinert application), and an upper movable part or assembly A2 consisting of cross lamination C4 and legs L4, L5 and L6. The upper part A2 may be moved by means of cross bar 12 from rods 14 and 16. The rods are rotatable and the upper part A2 may be moved upwardly and downwardly as the rods are rotated so that the spacing between the movable legs L4, L5, L6 and the fixed legs LS1, LSZ, LS3 and the reluctance of @the core varied.

The primary windings P1, P2, P3 are mounted on the litixed core CF encircling the legs L1, L2, L3, respectively. 'The secondary reactor windings SR1, SR2 and SR3 in- 'clude a number of turns wound about sets of legs L1 and L4 and LS1, L2 and L5 and L82 and L3 and L6 and .LS3, respectively, of the fixed and variable cores, the remaining turns being wound only about the legs L4 and LS1, L5 and LS2 and L6 and LS3 of the variable core. vWhile all of the turns of the secondary-reactor cooperate to produce the desirable electrical features of the arc welder thus far disclosed, I will, only forthe purpose of Adistinguishing between the two groups of turns in this discussion, call the turns wound about the legs of the :fixed and variable reluctance cores the secondary turns or the secondary and the turns wound about the legs of the variable reluctance core only the reactance turns or :the reactor.

The electrical apices 201, 2&3, 205 of the primary delta network are connected to the buses Ki, K2, K3 through the contactors 207, 209, 211, respectively, of a circuit interrupting means 1C, such as a circuit breaker. The -circuit interrupter IC preferably is of the shunt-trip type known in the art as the AB circuit breaker. Such a Vbreaker has in addition to the components just described a trip mechanism MT, actuable by a trip coil or solenoid 221. The interrupter IC is also provided with a resetting handle RE which extends through the wall of the cabinet 17.

The coil 221 is in accordance with my invention adapted to be connected between the apices 201 and 205 through the normally open contacts 223 and 22S of a thermal switch ST, such as a Thermoguard thermostat, and a normally closed push button 227. The actuating bimetal 229 of the switch ST is in intimate contact with the secondaries of one of the secondary-reactor windings SR2. As shown in Figs. 5 and 6, the thermostat ST is enclosed in an insulating container 231i which is usually composed of a phenolic condensation product. The container is mounted in a tube 233 of glass or like material and the tube is inserted between two turn layers 235 and 237 of the secondary (SR2). The tube 233 extends well over the container 231 and above the layers 235 and 23'7 to provide a long electrical leakage path between the terminals 239 and 241 of the thermostat ST and the turns. The transformer is dipped in varnish and baked after the thermostat ST is inserted. Care must be taken to prevent the leakage of varnish thro-ugh the container 231. Such varnish may cause contacts 223 and 225 to stick. Leakage may for example be prevented by spraying a quick drying paint over the surface of the container 231.

The conductors K1, K2 and K3 are supplied from the usual commercial supply which may have various voltages, such as 220, 440, 550 and other higher voltages.

f "'-The Aapparatus disclosed' in. the.- drawings -.also-includes a `rectifier assembly 56- which includessix units 56a, 56b, H5`6c,'56al,'56e and'56f. The units 56a through 56j are mountedin pairs 56a and 5.6b, 56C and 56d, and 56e and 5'61 on rods 241, 243, 245 which are securedto channels 60. QThe channels 60 are secured to angle brackets 62 fastened to the base offthe container 17. The units 56a throughvSf `are well spaced so that airmay be circulated lthroughthem' readily for cooling.

"Eachunit 56a through 56]? consists of a stack of dry rectifiersf2'51 each ofrectangular section. The rectifier .plates`253 are..spaced a substantialdistance as shown for unit56fso as to` permit them to cool effectively. The

, plates. themselvesserve as fins to conduct'thel heat from the rectifying basesof thedry rectifier elements.

yTherectifier units 4 56a through 56f are preferably, .although not necessarily, of the selenium type. Such unitsused in the1preferred practiceV of my invention con- :sist' of an aluminumjplate 253,such as .isshown Vin the drawing, which( is nickel plated and onl one surface of which a layer of selenium is deposited. Near the center of the plate onthe selenium, a layer of cadmium sulphide -is deposited and. on thecadmium sulphide a layer of cadmium-tin alloy isdeposited. 'The rectification. effect. is produced between the cadmium tin alloy and the selenium andlithe. terminalsof lthe rectifier are connected to vthe aluminumv and tothe cadmium tin alloy.

' In'the practice of my invention, the rectifier units. 56a through'if are connected in a so-called bridge network. `A,positive.terminal of units 56a, 56C and 56e and a nega- ,ti-ve terminal of units 56b, 56d and56f are connected re- ,spectively by a common conductor 259, 261 and263 to an apex 301,303 and 305 of the'delta secondary-reactor circuit. Thei negative terminals of the units 56a,. 56e and 56e areall connected .to a common conductor 307 which 'is connectedl to 'the welding electrode"E. The positive `terminals of. theother units. .56th-"56d and. 561 are. connectedto a common vconductor 309 to the workW.

The transformer TR and therectier S6 are,..in accord- -ance with' the practice of my invention, sodesignedas to supply an ,open-circuit voltage of-70 betweenftheelec Vtrode, E andthe wo\rk`W,and to supply between-8amperes i and1`600 amperesin a weldingoperation.

' The apparatus is provided with. a fan 79 drivenby a motor'81 whichis connected yacross apair of apicesv 201 -and`203 of the primary circuit. The fan supplies cooling air throughv the transformer TR and the rectifier 56.

In' the 'operation of the apparatus,V theV circuit .interrupterICis closed and power issuppli'edfrom they buses K1, K2, andfKS. tothe primary. circuitvand through it to the secondary-reactor circuit andthe vrectifier 56 and between the windingfelectrode E and the work W. The `apparatus is set' for a'welding operation by. adjusting themovable assembly A2 of thevariable reluctance core so that thev secondary yreactor units SR1, SR2 and SRS have the necessary reactance. In producing a'weld, the operator brings the electrodeE into engagementwith the workW for a shortt-ime interval and then separates vthe electrode from the work to produce an arc. Theewelding operation may then proceed.

The setting of the movable assembly A2 determines the impedance of the secondary-reactor windings SR1,

' SR2,.SR3 and thus determines the magnitude of the weldling current. `The secondaryreactor. windings absorb a portion of the impressed voltage depending on thesetting of the assembly A2. Sincethese windings areconnected in1 a delta network, the energy resultingv from the .action of'the secondary-reactor windings is dissipated in the network and tofan extent tothe windings. But solong as the weldingoperation proceeds normally, the thermostat ST, `although it is heated, is not sufficiently .heated to closeits contacts 223 and 225. Thecircuit interrupter 1C. then remains' in closed position.

Abnormalities in the operation requiring operation of the interrupter-IC may occur under various conditions.

To measure `the temperature of the transformer cornponents, the windings -of 4thel components were wound vAmong these, the principal conditions are that the' blower "79-'81 may stop operating or may operate ineffectively,

the operator may hold the electrode E in engagement with the work W for an'excessive. time interval, or the welding may be carried out at a duty cycle higher than that for which the apparatus is rated or at .higher than rated current.

shows theactual temperature variations of the various components of the apparatuswith vthe fan on and off as a'function of time. Thecurves which are labelled to correspond to the various components wereV prepared ope'ratinga 300ampere Welder, as disclosed. herein, from a cold start at an ambient temperature of 25 C. The welder was operated continuously under short-circuit load conditions drawing' approximately 232 amperes. The temperature hmeasuring devices vwere thermocouples. To measure lthe rectifier temperature, a number of such thermocouples were distributed on the rectifier assembly.

with thermocouples inserted between them. Thermocouples wereinserted between turnsof Athe primary windings'fPL P2,P3; at least one thermocoupleV was inserted between thev turns ofthe portion'of the secondary-reactor winding vwhich is wound about both cores CF and CV l(called secondary above); and at leastone thermocouple was inserted between the turns of the portion of the secondary-reactor vwinding which is lwound only about the variable reluctance core CV' (called reactor).

'In Fig. 7, thel temperature lrise of each component in 'centrigrade degrees Ais plotted vertically and the'time of operation of the apparatus is plotted horizontally. The four curves aslabelled are `the curves for the rectifier56,

' the secondary portion of-the secondary-reactor SR1, SR2,

SRS, the' reactor portion of the secondary-reactor, and the primary P1, P2, P3.

fItisvseen that starting from cold start with the vfan -79 on, the temperature rise of the rectifier levels off at `about 31 .after a' time interval of approximately`five minutes. This condition arises because the rectifier 56, while of light weight, includes facilities for increasing the effectiveness of itsheat emission. The spacingfbetween the units 56a through 56]c is substantial, and the plates. 253 are also well spaced. The operation of the fan. 79 then quickly draws the heat away from the internal parts ofthe rectifier where it is generated.

Thetemperature of the reactor portion of the secondary-reactor, the secondary portion of the secondary reactor, and the primary level off at temperature rises of 67, 75 and 80 between 40- and '50 minutes after the operation vis started with the fan on. These components yare oflarge mass and absorb heat slowly. They rise to va substantial temperature before leveling ofi .because the heat developed inthese components is developed in close proximity to the turns and because of the construction of the windings they arenot effective emitters of heat developed.

The leveling yoft' temperatures of the rectifier 56, the secondary, and the reactor and the primaries P1, P2, P3 are, according to my findings, substantially lower than the danger temperatures for these components. I have found that'the danger temperature for the rectifier 56 is C. (or 100 rise'over 25 C. ambient). andthe danger temperature for the components of the transformer-reactor TR is C. (or 125 rise over 25 C. ambient). lt is seen that during normal operation, the temperature rises of approximately 31 C. for the lrectilier 56, 67 C. for the reactor, 75 C. for the secondary and 86 C. for. the primary'are substantially lower'than the danger temperatures, and it is for .this .reason that .the thermostat ST remains open and the circuit breaker irernains closed during'normal operation.

. giving up its heat even with the fan turned off.

interrupted, is also shown. It is seen that the rectifier' 56 rises in temperature rapidly and at a higher rate than with the fan on, once the fan is turned off. The increased rate of rise occurs because the rectier by reason of its structure and its mounting near the base of the cabinet 17 is particularly well adapted to be cooled by the fan. Once the fan is turned off, this effective cooling is removed and the rectifier, being of light weight, quickly manifests the influence of the heat which is supplied to it. But the rise in temperature does not continue to a high rate. Because of the open construction of the rectifier 56, it is capable of effectively emitting or It is for this reason that the heating curve for the rectifier begins to level ofi" at approximately 53 temperature rise. The primary, secondary and reactor windings also rise in temperature after the fan is turned off, the secondary rising at a higher rate than the others. The rise in temperature of these components does not level off and appears in fact to increase in rate. This condition arises because the winding components are relatively ineffective emitters of heat. The secondary rises at a higher rate than either the reacto-r or the primary, because not only is it subject to the heat developed by the current flow through its own windings, but it also absorbs a large proportion of the heat developed in the reactor windings. This condition arises because the secondary-reactor windings SR1, SR2, SRS are connected in delta and the energy absorbed by the reactor in maintaining the voltage between the electrode and the work circulates through the secondary windings and is to a large extent absorbed in them. Since the secondary rises in temperature at the highest rate, the most effective protection is afforded by controlling the interrupter IC from the secondary, and for this reason the thermostat ST is mounted in intimate thermal contact with a nurnber of the secondary turnsy of the secondary-reactor winding SR2 and is set to operate when the temperature of these turns rises to a magnitude well below their danger temperature. This temperature is well below the danger temperature for the other components of the apparatus.

If then an overheating condition simulating the turning off of the fan 79 occurs, or the fan 79 is'actually turned off, the secondary (SR2) reaches a temperature at which the thermostat ST operates, contacts 223 and 225 engage closing the circuit through the trip coil 221 and permitting the interrupter IC to drop out. The supply to the primaries P1, P2 and P3 is then interrupted, and since the rectifier 56 is at this time well below its danger temperature, it, as well as the transformer-reactor TR is protected by the opening of the interrupter.

The opening of the interrupter IC opens the circuit of motor 81 and turns off the fan. The cooling of the thermostat ST and the opening of the contacts 223 and 225 is then delayed for an appreciable time interval. The push button 227 is provided to permit reclosing of the interrupter tC before the contacts 223 and 225 have opened. To reclose the interrupter, the button 227 is held open holding open the circuit through the trip coil 221, and the handle RE is operated to close the interrupter. The interrupter then remains closed so long as the button 227 is held open, even if the contacts 223 and 225 are still closed. The fan is then turned on and cools the thermostat ST so that the contacts 223 and 225 are opened.

In the apparatus on which Fig. 7 is based, the thermostat ST was set to operate at approximately 115 C. rise. Hence, when the secondary reached this temperature, the thermostat closed, closing the circuit through the trip co-il 221 of the circuit interrupter IC and permitting the later to drop out and to interrupt the supply of power to the apparatus. Since the interruption occurred when the secondary turns were at approximately 115 C. rise, it occurred when the primary turns were at 113 C. rise, when the reactor turns are at 97 C. rise, and when the rectifier was at 54 C. rise. The circuit breaker then opened well before any of the components had reached a danger temperature.

Fig. 7 was produced with a short circuited load and presents the manner in which the temperature of the various components vary under such conditions. It appears that for too high a duty cycle or excessive load current with the fan either -on or off, the variation would be of the same character as that shown in Fig. 7. Under these circumstances then the secondary turns of the secondary-reactor winding SR2 or of the other secondaryreactor windings SR1 or SRS would rise at a substantially higher rate than the other components and the operation of the thermostat when these turns reach a predetermined temperature below the danger point for these turns would also afford protection for the other components.

If all or a large portion of any primary winding P1, P2 or P3 were short circuited, the power line fuses (not shown) would operate to disconnect the supply. If all or a large portion of a secondary-reactor winding SR1, SR2 or SRS were short circuited, high current would be induced in the corresponding primary P1, P2 or P3 and again the fuses would blow.

Thus, I have provided an arc Welder in which a thermally actuable element disposed to respond to the temperature of the transformer reactor TR affords cornplete protection for a direct-current arc Welder. The temperature at which the thermally actuable element operates is critically indicative of the temperature of the other components of the apparatus and is reached well before the other temperatures are at a danger point. The thermally actuable element thus operates to protect the apparatus against overheating or overloads.

While I have shown and described a certain specific embodiment of my invention, many modifications thereof are possible. Thus the thermostat ST may be embedded in one of the primaries P2 as shown in Fig. 8 rather than in the secondary reactor SR1, SR2, SRS. This modification has certain advantages over the embodiment in which the thermostat ST is disposed in a secondary reactor winding. The contacts 223 and 225 of the thermostat ST are connected in series with the coil 221 which is connected across the primary P2. Thus the thermostat which has the line voltage (usually 230 volts) in it is nested in the primary P2 which has the same voltage in it. The thermostat ST is also thus located in the primary side of the major insulation 401 (usually a phenolic condensation product) thus minimizing the probability of insulation failure between the primary electrical parts and the secondary electrical parts. This is important for safety means because the operator is connected to the secondary parts when he is holding the welding electrode. My invention, therefore, is not to be limited except insofar as is necessitated by the spirit of the prior art.

I claim as my invention:

1. An arc welder comprising a transformer having a primary and a secondary, rectifier means connected to said secondary, means for connecting said rectifier means to a welding electrode and work and Vcircuit interrupting means connected to said primary to interrupt the power ow to said primary, said rectifier means and transformer being of the type in which in the event of abnormal conditions requiring operation of said interrupting means the temperature of said rectifier means tends to level off before it reaches a dangerous condition while the temperature of said transformer rises at a substantially higher rate than the temperature of said rectifier means, said arc welder being characterized by thermally actuable means embedded in said transformer in intimate thermal contact with a winding thereof and connected to said circuit interrupting means for actuating said interrupting means when the temperature of said Welder becomes excessive.

.2. -In-- combination, a. ...transformer for Vconnection Y to. a

.commercial power supplyhavingafprimary and a secondvary,lcircuit interruptingmeans;connectedto said primary forinterrupting the'powerfiowtoesaid primany, dryrec- .tifier ,Y means e connected to said secondary forsupplying ,direct-current.powerand thermally `actuablemeans con- -eventof abnormal;conditions-requiring the operation of tsaid interrupting means,theltemperature of saidrectifier means tends to level-off before-it reaches afdangerous condition. Whilethe temperatureof-the transformer-rises;

at `a substantiallywhigher'rate -than-'the temperature of -`said rectifier means 3. In combination, atransformer for connection to a commercial power vsupply 'having a primary and a secondary, circuitinterrupting means connected to saidprimary for interrupting the power floW to said primary, dry rectifier means connected to said secondary for `supplying direct-current power and thermally actuable means connected to said circuit interrupting means and embedded in said secondary in intimate thermal contact With a turn of said secondary, said rectifier means and transformer being of the type in which in the event Aof abnormal conditions requiring the operation of said interrupting means, the temperature of said rectier means tends to level off before it reaches a dangerous condition While the temperature of said secondary rises at a substantially higher rate than the temperature of said rectifier means.

4. An arc Welder comprising a transformer having a primary and a secondary, rectifier means connected to said secondary, means for connecting said rectifier means to a Welding electrode and Work and circuit interrupting means connected to said primary to interrupt the power flow to said primary, said rectifier means and transformer being of the type in Which in the event of abnormal conditions requiring operation of said interrupting means the temperature of said rectifier means tends to level off before it reaches a dangerous condition While the temperature of said secondary tends to rise at a substantially higher rate than the temperature of said rectifier means, said arc Welder being characterized by thermally actuable means embedded in said secondary of said transformer in intimate thermal contact With a turn of said secondary, said thermally actuable means being connected to said -circuit interrupting means for actuating said interrupting means When the temperature lof said Welder becomes excessive.

5. An arc Welder comprising a transformer having a primary and a secondary, rectifier means connected to said secondary, means for connecting said rectifier means to a welding electrode and work and circuit interrupting means connected to said primary to interrupt the power fioW to said primary, said rectifier means and transformer being of the type in Which in the event of abnormal conditions requiring operation of said interrupting means the temperature of said rectifier means tends to level off before it reaches a dangerous condition, said secondary rising in temperature at a higher rate than the other Windings of said transformerand at a substantially higher rate than that of said rectifier means in the event of said abnormal conditions, said arc Welder being characterized by thermally actuable means embedded in said secondary of said transformer in intimate thermal contact With a turn `of said secondary, said thermally actuable means being connected to said circuit interrupting means for actuating said interrupting means when the temperature of said Welder becomes excessive.

6. In combination, a transformer of the polyphase type for connection to a commercial power supply having a primary and a secondary-reactance including variable reactance means, means connecting said secondary-reactance in a polygonal circuit so that the energy absorbed :by-said Arc'eactance means Ycirculates,,and is;absornad'ibs/,ly

`said ycircuit,-circuit interrupting means connected-tto=-siaidl `primary for interrupt-ing `the v.power yiiow lto .said primary, dry rectifier 'means f connected to saidsecondary-reactance' .for supplying directcurrentpower andithermally aetua'ble .means-.Connectedto5said circuit interruptingmeans vand embeddedin saidsecendary reaetancein intimate thermaf 4contact with' a- :turn :of said secondary reactance, said trectifier:meansfandttransformer beingfof the'type inwhich in the event-.of-abnormal conditions vrequiring the operation of saidnterruptingpmeans lthe temperature of said frectitier .means tendsg .to level off 'before Lit reachesv a dangerous condition ,and `the temperature -off;'saidfsecondyary tendsrto'lrise atasubstantially higher rate `'than the `temperature of ,said rectifier means.-

07. In combination, a polyphase transformer havingfa primary andvapolyphasel secondaryfeonnecteddn al po-v lygonal network,` .electrically actuable coolingl means con- .nected tol-saidtransform1er for fcoolingfsaid transformen,

a circuit interrupter connected to said primary to interrupt the current ow to said primary and to said cooling means, said interrupter having -a normally open trip circuit Which is closed to actuate said interrupter to interrupt, rectifier means connected to said secondary, said rectifier means and transformer being of the type in Which the event of abnormal conditions requiring operation of said interrupting means, the temperature of said rectifier means tends to level off before it reaches a dangerous condition While the temperature of said secondary tends to rise at a substantially higher rate than the temperature of said rectifier means, a thermally actuable element embedded in said secondary in intimate thermal contact only With one Winding of said secondary, connections between said element and said trip circuit for closing said trip circuit When the temperature of said one Winding becomes excessive, and switch means in said trip circuit for opening said trip circuit independently of said thermally actuable element.

8. An arc Welder comprising a transformer having a primary and a secondary, rectifier means connected to said secondary, means for connecting said rectifier means to a Welding electrode and Work and circuit interrupting means connected to said primary to interrupt the power flow to said primary, said arc Welder being characterized by thermally actuable means embedded in the primary o-f said transformer in intimate thermal contact With a Winding thereof and connected to said circuit interrupting means for actuating said interrupting means when the temperature of said Welder becomes excessive, said transformer and rectifier being of the type in which in the event of abnormal conditions requiring operation of said interrupting means, the temperature of said rectifier means tends to level off before it reaches a dangerous condition While the temperature of said primary tends to rise at a substantially higher rate than the temperature of said rectifier means.

9. An arc Welder comprising a transformer of the polyphase type having a plurality of phase windings having a primary and a secondary, rectifier means connected to said secondary, means for connecting said rectifier means to a Welding electrode and Work and circuit interrupting means connected to said primary to interrupt the power tioW to said primary, said arc Welder being characterized by thermally actuable means ernbedded in said transformer in intimate thermal contact With one of said phase windings, and circuit means including said thermally actuable means connected to said circuit interrupting means and also connected across said one phase Winding to derive power from the potential across said phase Winding for actuating said interrupting means when the temperature of said Welder becomes excessive, said transformer and rectifier means being of the type in which in the event of abnormal conditions requiring operation of said interrupting means, the temperature of said rectifier means tends to level off before it reaches a dangerous condition while the temperature of said phase windings tends to rise at a substantially higher rate than the temperature of said rectier means.

10. An arc Welder comprising a transformer having a primary and a secondary, electrically actuable cooling means connected to said transformer for cooling said transformer, rectiier means connected to said secondary, means for connecting said rectier means to a welding electrode and work and circuit interrupting means connected to said primary and to said cooling means to interrupt the power flow to said primary and to said cooling means, said rectifier means and transformer being of the type in which in the event of abnormal conditions requiring operation of said interrupting means, the temperature of said rectifier means tends to level off before it reaches a dangerous condition while the temperature of said transformer rises at a substantially higher rate than the temperature of said rectifier means, said arc Welder being characterized by thermally actuable means embedded in said transformer in intimate thermal contact with a winding thereof and connected to said circuit interrupting means for actuating said interrupting means when the temperature of said Welder becomes excessive and manually actuable means connected to said circuit interrupting means when actuated conditioning said interrupting means to permit power ilow to said transformer independently of said thermally actuable means.

References Cited in the le of this patent UNITED STATES PATENTS 1,959,513 Weyandt May 22, 1934 2,112,093 Harty Mar. 22, 1938 2,125,110 Harty July 26, 1938 2,471,840 Seely May 31, 1949 2,518,597 Brooks Aug. 15, 1950 2,523,117 Jennings Sept. 19, 1950 FOREIGN PATENTS 156,266 Germany Jan. 15, 19391. 

